The drill screams!
A customer brought me a Specialized EPIC frame to work on.
The threads on the through-axle hole had stripped,
and they couldn't secure the rear wheel anymore.
In the photo above, I've already removed the aluminum derailleur mounting dropout.
Since EPIC is a full-suspension frame,
it can be split into the front triangle and rear triangle (swingarm),
but Specialized's Japanese distributor only sells the swingarm separately
when they have it in stock.
Apparently, the swingarm in this photo is actually the second one
for this particular front triangle.
I suggested they just buy another one,
but they said there was no stock available, the price was high,
and they needed it ready for a race,
so I got their approval to attempt a helicoil repair as a temporary fix.
↑This is a photo from a different job, not the EPIC,
but it shows a 12mm through-axle with a pitch of 1.75mm—
an uncommon specification.
However, for M12 metric threads,
1.75 is actually the standard coarse pitch,
with 1.5 being fine pitch and 1.25 being extra-fine pitch.
The frame in question uses the X-12 specification I mentioned in an earlier post,
so the axle threads are 12×1.0mm.
This is finer than extra-fine pitch,
a special size that often doesn't even appear on standard thread charts.
Recoil (リコイル) makes kit sets with dedicated-size drill bits, taps, and helicoil insert tools
called "Recoil Kits." The three common sizes—12×1.75, 1.5, and 1.25mm—
each retail for around 10,000 yen, with street prices around 9,000 yen,
but the 12×1.0 isn't available through normal distribution channels
and is priced at exactly double the others.
Expensive, but I ordered it anyway.
12×1.0mm.
I also bought extra inserts separately as insurance in case I mess up,
and because I thought the inserts included in the kit were too short.
All told, it came to about 22,000 yen.
Separately from that, I also bought a 12×1.0mm tap.
This is such a special size that cheap versions don't exist.
Besides, I never buy cheap tools for work like this anyway.
Before buying the Recoil Kit,
I consulted my mentor,
and he said that for a 12×1.0mm hole, I could
just machine it out
and epoxy-bond a custom-machined aluminum bushing with a flange
that has 12×1.5mm threads tapped into it
(the flange ensures the wheel stays secured even if the adhesive fails),
and the 1.5mm pitch is less prone to thread stripping anyway.
However, I explained that since this is X-12 spec, the base of the through-axle is tapered,
so 12×1.5mm threads won't work.
I could potentially machine a part that fills the tapered section,
but that would be quite complicated.
So I decided to use the helicoil approach first,
and save that custom machining option as a last resort if things go wrong.
Whirrrrr.
I used the 12.2mm pilot drill that came with the Recoil Kit.
This was incredibly difficult—later, when my mentor asked if I'd succeeded,
he said "I'm impressed you managed to drill such a straight hole with a hand drill."
Since I'm not charging the customer for the full cost of all these tools,
I'd need to do this repair 2-3 more times to break even on the investment,
but honestly, I never want to do it again.
I tapped the hole to the insert thread size.
↑Like this
I installed the helicoil insert.
The original through-axle with the stripped threads had terrible engagement feel,
so I was concerned about its reliability.
I swapped it out for a DT (ディーティー) X-12 spec axle.
I asked the customer that when first threading the new axle,
if they feel any catching on the first thread, they should gently find the smooth engagement point
without forcing it (no pun intended—through-axle, after all).
It's been several months since I did this repair,
and the customer has apparently even used this frame in races,
but it's working perfectly with no issues so far.
A customer brought me a Specialized EPIC frame to work on.
The threads on the through-axle hole had stripped,
and they couldn't secure the rear wheel anymore.
In the photo above, I've already removed the aluminum derailleur mounting dropout.
Since EPIC is a full-suspension frame,
it can be split into the front triangle and rear triangle (swingarm),
but Specialized's Japanese distributor only sells the swingarm separately
when they have it in stock.
Apparently, the swingarm in this photo is actually the second one
for this particular front triangle.
I suggested they just buy another one,
but they said there was no stock available, the price was high,
and they needed it ready for a race,
so I got their approval to attempt a helicoil repair as a temporary fix.
↑This is a photo from a different job, not the EPIC,
but it shows a 12mm through-axle with a pitch of 1.75mm—
an uncommon specification.
However, for M12 metric threads,
1.75 is actually the standard coarse pitch,
with 1.5 being fine pitch and 1.25 being extra-fine pitch.
The frame in question uses the X-12 specification I mentioned in an earlier post,
so the axle threads are 12×1.0mm.
This is finer than extra-fine pitch,
a special size that often doesn't even appear on standard thread charts.
Recoil (リコイル) makes kit sets with dedicated-size drill bits, taps, and helicoil insert tools
called "Recoil Kits." The three common sizes—12×1.75, 1.5, and 1.25mm—
each retail for around 10,000 yen, with street prices around 9,000 yen,
but the 12×1.0 isn't available through normal distribution channels
and is priced at exactly double the others.
Expensive, but I ordered it anyway.
12×1.0mm.
I also bought extra inserts separately as insurance in case I mess up,
and because I thought the inserts included in the kit were too short.
All told, it came to about 22,000 yen.
Separately from that, I also bought a 12×1.0mm tap.
This is such a special size that cheap versions don't exist.
Besides, I never buy cheap tools for work like this anyway.
Before buying the Recoil Kit,
I consulted my mentor,
and he said that for a 12×1.0mm hole, I could
just machine it out
and epoxy-bond a custom-machined aluminum bushing with a flange
that has 12×1.5mm threads tapped into it
(the flange ensures the wheel stays secured even if the adhesive fails),
and the 1.5mm pitch is less prone to thread stripping anyway.
However, I explained that since this is X-12 spec, the base of the through-axle is tapered,
so 12×1.5mm threads won't work.
I could potentially machine a part that fills the tapered section,
but that would be quite complicated.
So I decided to use the helicoil approach first,
and save that custom machining option as a last resort if things go wrong.
Whirrrrr.
I used the 12.2mm pilot drill that came with the Recoil Kit.
This was incredibly difficult—later, when my mentor asked if I'd succeeded,
he said "I'm impressed you managed to drill such a straight hole with a hand drill."
Since I'm not charging the customer for the full cost of all these tools,
I'd need to do this repair 2-3 more times to break even on the investment,
but honestly, I never want to do it again.
I tapped the hole to the insert thread size.
↑Like this
I installed the helicoil insert.
The original through-axle with the stripped threads had terrible engagement feel,
so I was concerned about its reliability.
I swapped it out for a DT (ディーティー) X-12 spec axle.
I asked the customer that when first threading the new axle,
if they feel any catching on the first thread, they should gently find the smooth engagement point
without forcing it (no pun intended—through-axle, after all).
It's been several months since I did this repair,
and the customer has apparently even used this frame in races,
but it's working perfectly with no issues so far.